The present invention relates to cyclone combustor apparatus for burning ultra-fine coal particles. In particular, this invention relates to a cyclone combustor for burning micronized coal particles or a coal-water slurry of micronized coal particles. More particularly, this invention relates to such a cyclone combustor which has a low thermal input which makes it suitable for use as a heating unit for a single-family dwelling, for a small industrial building, for a small retail sales establishment, and the like.
Many apparatus designs for the combustion of pulverized coal particles are known in the art. In general, they take the form of a fixed fluidized bed or a circulating fluidized bed, and they are designed for high thermal inputs such as that required for service as a public utility steam generator.
Cyclone coal combustors are also known in the art. A cyclone coal combustor is, in general, a horizontal cylindrical device into which pulverized coal is injected with primary air, the air-coal mixture then being centrifuged with secondary air toward the cylindrical wall of the cyclone combustor. When coal particles burn while in the air suspension or on the wall of the cyclone combustor at hot oxidizing temperatures, such as at an average temperature of about 3000.degree. F., the ash particles in the coal melt. Those ash particles which are in the gas suspension are melted and thrown to the wall by the centrifugal force within the cyclone coal combustor. This liquefied ash, called slag, rapidly coats the wall and is continuously drained by the action of gravity toward the bottom of the cylindrical combustor chamber and it is collected at a position downstream of the inlet end of the chamber. In conventional practice it is then removed through a port called a slag tap. Such a cyclone coal combustor is illustrated in U.S. Pat. No. 4,624,191. This cyclone coal combustor is also generally oriented toward high thermal inputs of from about 1 million BTU per hour to about 100 million BTU per hour.
It is an object of the present invention to provide a coal combustor having a low thermal input which makes it suitable for use as a residential heating unit and the like.
It is another object of the present invention to provide a coal combustor having a high combustion efficiency.
It is a further object of the present invention to provide a low capacity coal combustor which has a high turndown ratio.
These and other objects of the invention, as well as the advantages thereof, will become clear from the disclosure which follows.